The goal of this project is to specify the role of endocrine factors in determining submissiveness -- the readiness of an individual to surrender following attack. Two kinds of relationships are studied here: 1) the role of the individual's hormonal state prior to entering the competitive situation, the baseline hormonal state, in determining submissive responses, and 2) the role of the hormonal responses to defeat in mediating the effects of that experience on subsequent submissive reactions. Two approaches will be used in this project. In studying the first relationship, the animals will be subjected to a range of hormonal manipulations prior to exposing them to aggressive opponents. In studying the second relationship, the individual's hormonal responses to defeat will be altered by hormonal manipulations made immediately following an initial defeat and, then, the individual's subsequent submissive reactions will be studied. This project will increase our understanding of the role of endocrine factors in determining competitive characteristics.